Small, cationic antimicrobial peptides (AMPs) are naturally occurring antibiotics of the innate immune system. AMPs are widely distributed in animals and plants and are among the most ancient host defense factors. Their spectrum of activity includes Gram-positive and Gram-negative bacteria as well as fungi and viruses. As resistance of pathogenic microbes to conventional antibiotics increases, researchers are exploring these endogenous antibiotics as a potential source or new therapies against variety of infectious diseases.
Virus infections occur following entrance of virions into host cells by a variety of mechanisms including endocytosis of non-enveloped viruses and fusion with the cell membrane by enveloped viruses. One primary barrier to the infection is epithelial keratinocyte of the skin. Alterations in skin barrier function are seen in atopic dermatitis (AD). This finding may contribute to infection with bacteria and selected viruses, including Herpesviridae (herpes simplex virus (HSV), varicella-zoster virus) and vaccinia virus. However, it is unlikely that a defect in the physical barrier alone accounts for the remarkably increased susceptibility of AD patients to recurrent skin infections. Patients with plaque psoriasis, a common Th1-mediated inflammatory skin disease also associated with skin barrier dysfunction, do not have increased susceptibility to microbial skin infection.